After I first built my MPCNC, the middle assembly was pretty square. However, after some use, several bearings got a bit loose. I tightened them up, but now my middle assembly is no longer square. The X axis is perfectly perpendicular, but the Y axis is off 8.5mm on one end (over a distance of almost 1000mm).
As I understand it, I have a couple of options:
- Fiddle with the middle assembly tension bolts until it's square again. I think that would require some bearings to be very loose or some to be very tight.
- Force the gantry to be square before I turn on the steppers. (Or use dual endstops to automate this). However, even by hand I need a relatively large force to push the Y axis so that it stays square. The steppers can hold it in place, but then I have less torque left over and more risk of skipping steps when cutting things.
- Correct for the skew in the firmware or gcode. I printed a small ring of 8.5mm wide that I put on the skewed Y axis, so that I can reliably get the same skew every time.
So, my plan is to write a small gcode postprocessor which corrects for my particular skew.
My question is, does this sound reasonable? Has it been done before? Or should I just go for option 1 and correct my middle assembly?